Graphic representation of configuration in two-dimensional space. Current conventions, clarifications, and proposed extensions

Calcitriol derivatives with two different side chains at C-20. 24-hydroxy derivatives as metabolic products and molecular probes for VDR exploration

We previously synthesized calcitriol derivatives with two identical side chains emanating at C-20, also known as gemini. In view of the evidence identifying C-24 hydroxylation as the first step in the in the metabolic cascade of calcitriol and gemini, stereochemical differentiation between the possible epimeric 20R- and 20S side-chain hydroxylated gemini became of interest. We now report the stereoselective synthesis of these compounds. Of these, 1,24(R),25-trihydroxy-21-(3-hydroxy-3-methyl-butyl)-20(R)-19-nor-cholecalciferol was identified as the main metabolic product of 19-nor-gemini. In general, higher doses of the 24-hydroxylated gemini compounds were required to increase blood calcium levels in mice and to suppress INF-gamma release in MLR.

Automated Drawing of Structural Molecular Formulas under Constraints

In this paper, we present a new algorithm for automated drawing of 2D structural formulas of molecules. The algorithm is based on the classical scheme of a drawing queue placing the molecular fragments in a sequential way. We extend the concept of so-called prefabricated units developed for complex ring systems to automatically created drawing units for chains and rings which will then be assembled in a sequential fashion. The approach is fast and can be naturally extended to the problem of drawing molecules with common core structures. Further on, we present an algorithm that allows the drawing of 2D structural formulas under directional constraints assigned to a subset of bonds. Since no numerical optimization is necessary, the algorithm creates drawings of small organic molecules on the order of 500 structures per second. The new algorithm is relevant for all kinds of prediction and analysis software presenting a large number of probably similar molecular structures to the user of the software.